If people are behind the expected performance due to incompetence, wasted time or poor self-management, then this is reasonable.
We are all adults here.
Insisting that your employees work weekends for months on end is obviously unacceptable. Asking your employees to work occasional overtime in certain circumstances hardly seems monstrous to me.
You can ask for a new version of the theory of relativity from the janitor by the end of the week, but if she fails to deliver I would not put the blame on her.
If it is employee laziness or incompetence, the employees should be retrained, demoted or fired. Grinding them on weekends is only likely to make the productivity drain worse and if they are creating bad work outputs, you’re accelerating the compounding growth of their mistakes.
I like what was said in Peopleware about this, “You can kick someone to make him sit up in his chair, but you can’t kick someone to make him work.”
Despite all of the above, 99% of the time this sort of issue stems from toxic & incompetent management. Is your CEO using Twitter to bark workload policy at you? Well, then you know who the problem is.
Also, do you think that (given, again, the general tone) that the management would evaluate a low-performing employee in a fair and objective way?
Even asking people to work on weekend without compensation it's illegal in many countries.